The present invention relates to photographic (e.g., radiographic) imaging, more particularly to methods, systems, and computer programs for processing or analyzing photographic images, for instance radiographic images of fast-moving objects such as shaped charge jet particles.
A conventional shaped charge device is a weapon designed to concentrate explosive energy in a focused manner. Detonation of a shaped charge results in a high-velocity jet of metal particles in a particular direction, some of which may be moving at hypersonic speeds. Notable are military applications of shaped charge technology as various forms of armor-piercing weaponry.
From a military standpoint, it is important to be able to implement flash radiographic images (e.g., x-ray photographs) to characterize the flight of shaped charge jet particles, and to do so with high degrees of accuracy and completeness. The radiographic image processing involved has much to do with the effectiveness of these characterizations.
The following references, each of which is hereby incorporated herein by reference, are instructive on previous radiographic image processing methods: H. John Blische, B. M. Simmons, “A Method for Reducing Data From Radiographs of Shaped Charge Jets,” U.S. Army Ballistic Research Lab, Aberdeen Proving Ground, Md., Technical Report ARBRL-TR-023330, June, 1981; Richard L. Summers, K. C. Wright, “Computer-Aided Analysis of Flash X-Ray Films,” U.S. Army Ballistic Research Lab, Aberdeen Proving Ground, Md., Technical Report BRL-TR-3393. September, 1992; James D. Pham, E. L. Baker, S. DeFisher, “Shaped Charge Jet Flash Radiograph Digitization,” U.S. Army Armament Research, Development and Engineering Center, Picatinny, N.J., Technical Report ARAET-TR-05013, September, 2005, Himanshu Shekhar, “Theoretical Modelling of Shaped Charges in the Last Two Decades (1990-2010): A Review,” Central European Journal of Energetic Materials, Volume 9, Number 2, 2012, pages 155-185.
One previous method for radiographic image processing of shaped charge jet particles requires the user to select digitization points on a jet particle's perimeter by hand. This approach lacks the consistency of any physical basis for choosing these digitization points, and will vary from user to user. Another previous method uses a computer code to choose digitization points automatically, but does not allow for any adjustment or visual verification by the user; in particular, the user has no input into the accuracy of the chosen locations.
Previous radiograph processing methods typically specify a predetermined number of points to be digitized for each jet particle, normally one to eight points depending on the location of the jet particle relative to the tip or lead particle. The geometric coordinates of these points are the principal data used in calculation of a jet particle's volume, length, mass, and velocity. More specifically, the volume characteristics and therefore the mass characteristics (mass is a function of liner density and volume) of the jet particle are determined from the summation of truncated conical segments created by these digitized points. These known methods give an approximation of the jet particle area, as the particle boundary is estimated by the line segment that connects two adjacent digitized points. As the number of digitized points is increased, the lengths of the corresponding line segments tend to zero, and hence the estimated boundary tends to greater exactitude.
Since shaped charge weapons are usually designed with a nearly optimized built-in standoff distance upon detonation, previous researchers have not been concerned with the full three-dimensional characterization of the jet. The axial velocity of the jet particles is the primary contributor to the penetration of the weapon, and the axial velocity measured in a two-dimensional image will be almost exactly the same as if performed in three-space. For this reason, previous methods do not account for vector-based relative motion. Nevertheless, this traditional lack of consideration of three-dimensional characteristics of jet particle flight neglects important phenomena of shaped charge weapons.